Water Supply Summary#
Water Supply#
Metro Vancouver Water Restrictions
Metro Vancouver is currently in Stage 2 water restrictions as of August 4. Click here for more information.
Metro Vancouver’s drinking water supply remains within the normal range for this time of year, but is lower than the last few summers. This is largely thanks to a healthy seasonal snowpack. Snowmelt kept reservoirs topped up until late June despite very dry conditions. 2015 is often used to show the impact of extreme dry weather conditions on water storage. The main difference in 2015 was an almost complete lack of seasonal snow.
The sub-alpine reservoirs were opened this summer to move more water into the primary reservoirs. This also increases flows and cools the waters in the rivers. Palisade Lake was opened on July 14 and closed on August 28 (and again briefly in September), Burwell Lake opened on July 26 and closed on Sep 22, and Loch Lomond was opened from August 17 to Sep 29.
Daily water consumption was high for most of the spring and summer due to persistent warm temperatures and drought. Demand decreased in August as temperatures cooled slightly and stage 2 water restrictions were implemented. Water conservation is critical to ensure adequate drinking water supply later this season. We can’t bank on the fall rains arriving early and replenishing our water reservoirs. Click here for tips on how to conserve water at home.
Fig. 11 Seymour Reservoir in late 2023. Photo: Metro Vancouver#
Snowpack#
As mentioned, this season’s snowpack climbed to near-normal levels on May 1st. However, the snowpack melted away rapidly under hot and dry conditions in May. Most of the snowpack disappeared during this month. This rapid melt caused reservoir’s to stop-spilling a few weeks earlier than normal. As you can see in the graph below, the second half of this snow season was very different than last year. The healthy spring snowpack this year may be a very important factor in the region’s water supply as we move further into the summer and early fall.
Below is a short clip showing the snowpack rapidly melting this past spring. It shows a daily image from the Orchid Lake weather station (Seymour Watershed) from April 24 until June 29. The snow depth was 430 cm on April 24, and had completely disappeared by the end of June.
Fig. 12 Disappearing Snow (Orchid Lake satellite camera)#
River Inflows#
Note
River inflows in the spring of 2023 were almost entirely from snowmelt. There was very little rainfall during the snowmelt season.
The plot below really highlights just how dry it’s been this year. It shows the cumulative river inflows (in billion litres) during the water year, which runs from October 1 to September 30 (WSC Station 08GA010). The red line is 2023, the blue line is 2022, the purple line is 2015, and the gray dashed line is the average of the past 20 years. For 2023, there is a sharp increase with the late December and early January storms, then again around Easter in response to heavy rain followed by rapid snowmelt in late April and May. The 2015 water year very wet in the fall and winter, but dried out in the spring and summer. This seasons drought came to an abrupt end at the end of August with the arrival of an early atmospheric river. There was 230 BL less inflow this water year than there was in 2015. This really highlights how important snow is for our summer water supply.
The next plot shows the average daily river inflows into the Capilano Reservoir. The solid red line is 2023, the blue line is 2022, the purple line is 2015, and the dashed black line is the average.
There is a notable increase in river flows in July 2015. This is a result of releasing water from the Palisade Lake reservoir early this season. River inflows in 2015 were very low because there was very little snowmelt runoff.
This year inflows were above average in May due to very warm temperatures and rapid snowmelt runoff. Inflows have gradually tapered off, and are now at very low levels for this time of year. Last year, prolonged drought caused river inflows to drop to record-low levels late in the summer, and remained very low until late October.
Water Supply Summary
The Lower Mainland is currently experiencing severe drought; however, Metro Vancouver’s source water supply remains within the normal range.
Water Temperatures#
River water temperatures are influenced by snowmelt runoff in the spring and early summer and air temperatures. Water temperatures are also influenced by rain events in the summer and early fall. Water temperatures typically drop significantly when water is released from the sub-alpine reservoirs (Palisade, Burwell, and Loch Lomond) in the late summer.
This year we have seen above average temperatures since late May, with near-record warmth in July. Temperatures cooled slightly in mid-July when Palisade Lake was partially opened. The warmest spring temperatures were observed in 2015 when there was essentially no seasonal snowpack. During this summer, river temperatures dropped by around 6 degrees when Palisade Lake was opened in July. The warmest late-season temperatures were recorded in 2022.
The graph below shows river water temperatures at Capilano Lakehead for 2023 (dark blue), 2022 (red), average (dashed black), the range of normal (gray shaded area), and the range of max and min (shaded blue).
Reservoir surface water temperatures are closely correlated with air temperatures. The average surface water temperature is typically very similar to the average daily air temperature. For 2023, we’ve seen above average surface water temperatures since late May, and during some periods temperatures have almost reached record levels. The graph below shows surface water temperatures for 2023 (dark blue), 2022 (red), average (dashed black), the range of normal (gray shaded area), and the range of max and min (shaded blue). Readings are taken at approximately 1 metre below the surface.